The present invention relates generally to radio access networks for mobile communication networks and, more particularly, to a signaling procedure to expedite access to the radio access network for radio resource control signaling.
Mobile wireless communication networks have achieved tremendous success in providing untethered voice communications but have had only limited success providing wireless data services. One obstacle for wireless data services is the limited peak data rates of second-generation wireless communication systems. Two of the most widely deployed communication standards, the Global System for Mobile Communications (GSM) and the Telecommunications Industry Association (TIA)/Electronics Industry Alliance (EIA) standard TIA/EIA-136, were both originally developed primarily for voice communications. Both the GSM and TIA/EIA-136 standards employ Time Division Multiple Access (TDMA) and circuit-switched technology and have limited data rates of about 9.6 kb/s.
To achieve higher data rates, General Packet Radio Service (GPRS) was developed as an extension of GSM and has been adapted for TIA/EIA-136 systems. GPRS employs variable-rate coding schemes and packet-switched technology to increase data rates to about 100 kb/s. However, still higher rates are needed to support web browsing and other popular applications. The target rate for third generation (3G) wireless services is 384 kb/s. Another limitation of GPRS is that it does not support voice services, which are still provided by the circuit-switched network. This service separation reduces potential spectrum efficiency gain resulting from multiplexing different services to the same radio channel.
The European Telecommunications Standards Institute (ETSI) has developed a new standard for GSM to support high rate data services. This new standard is known as Enhanced Data Rates for Global Evolution (EDGE). EDGE is an overlay for existing GSM systems and has been adapted for TIA/EIA-136 systems. One objective of EDGE is to provide voice services over the packet-switched network. EDGE systems employ higher-order modulation schemes and various link adaptations to obtain several hundred kb/s peak data rates. EDGE provides an evolutionary path from existing standards for delivering 3G data services in existing spectrum bands. EDGE allows rapid deployment, reuse of existing infrastructure in GSM and TIA/EAI-136 systems, as well as support for gradual deployment.
A GSM-EDGE radio access network (GERAN) uses two types of radio bearers in support of high rate packet data services: signaling radio bearers (SRBs) and user radio bearers (URBs). URBs are used to transmit user data (e.g., voice) from the mobile terminal to the GERAN. SRBs are used to transmit control signaling, such as radio resource control (RRC) messages, from the mobile terminal to the GERAN. The mobile terminal requires that the GERAN set up SRBs whenever a control signaling procedure, such as an RRC procedure, needs to be performed. Since control signaling is used extensively to establish, maintain, and terminate connections, an efficient mechanism is needed to minimize delays and reduce processing overhead associated with requesting and allocating control signaling (e.g., SRB) resources.
The present invention provides an expedited method for mobile terminals to obtain needed radio bearer resources from a radio access network (RAN). A radio bearer access request message transmitted by a mobile terminal indicates the mobile terminal""s need for radio bearer resources. The radio bearer access message may be a specific signaling radio bearer (SRB) resource request, or a generic radio bearer (RB) resource request.
SRBs are used for control signaling between a mobile terminal and a radio access network (RAN). The SRB-specific implementation of the RB access message comprises request type information identifying the access request type specifically as a SRB resource request, and further comprises resource type information identifying the specific type of SRB desired by the mobile terminal. This enables the RAN to make the necessary resource allocations to establish the specific type of SRB desired by the mobile terminal based on the single SRB access request message. SRB resource allocation delay is minimized because the mobile terminal transmits a single message, and radio resource control processing overhead at the RAN is reduced.
In the context of a GSM/EDGE RAN (GERAN), the SRB access request message permits an lu-mode capable mobile terminal to secure the specific type of SRB resource desired with a single message transmission on a shared packet channel resource. The 8 and 11-bit packet channel access request messages defined for GERAN may be modified to serve as SRB access request messages by including bit values specifying the message type as a SRB access request message, and additional bit values specifying the specific type of SRB desired.
By implementing the SRB access request message within the structure of the defined 8 and 11-bit packet channel access request messages, the SRB access request message is well suited to the contention-based RAN access procedures employed on the packet random access channels (PRACH) defined for GERAN. On a PRACH, many mobile terminals may be simultaneously competing for access to the RAN. Both the 8 and 11-bit versions of the SRB access request message complement operation in the bandwidth limited environment of a PRACH, where there may be limited opportunity for the mobile terminal to transmit to the RAN.
The more generalized RB access request message uses a similar one-phase RB resource request access, but supplies specific information about the type of RB resources being requested in one or more RLC data blocks transmitted by the mobile terminal once an uplink packet channel is assigned to it in response to the RB resource request message. Because the RB resource request message defines the request type as a RB resource request, the RAN is prepared to configure or otherwise identify the desired RB resources based on the subsequent RLC information from the mobile terminal.